Three years ago, 180 reef balls were placed in Lake Macquarie to assess how artificial reefs worked.

With marine life flourishing on the reef, a further 420 reef balls are set to be added.

The six reefs, each separated by 350 metres, will end up with 100 reef balls each.

"Recreational fishing groups have been so impressed with the reefs in Lake Macquarie, they have been calling to expand the project and that's what we plan to do," Mr Macdonald said.

"Two years of scientific monitoring of the artificial reefs have shown they have created valuable fish habitat, with more than 40 species of fish found living on the reefs."

Fish included yellowfin bream, snapper, whiting, flathead, yellowtail kingfish and amberjack.

The reefs are made of moulded concrete balls, which can be removed if necessary.

"Reef balls are made using a special mix of concrete that allows algae to grow quickly, creating ideal marine habitat for fish and invertebrates," Mr Macdonald said.

The project, which needs Lake Macquarie City Council approval, will be paid for with money from recreational fishing licence fees.

The reef's success has surprised some scientists.

Fisheries officers said the artificial reef was starting to mirror natural reefs.

The reef had become covered in many different types of algae, providing a plentiful food supply for fish.